A bearing used in an ordinary industrial motor, etc. may suffer from early damage due to high-voltage electricity flowing inside the bearing (hereinafter referred to as “electrolytic corrosion”). Conventional means for solving such problem include forming an insulating layer on at least one of an inner ring and an outer ring, so as to shutter the flow of current.
FIG. 17 illustrates an example of an insulated bearing having an insulating layer formed on an outer ring thereof. The insulated bearing 400 has an inner ring 403, an outer ring 405, and a rolling element (ball) 409, and an insulating layer 415 is formed on an outer circumferential surface 411 and axial end surfaces 413A, 413B of the outer ring 405 and includes a ceramic material. Since the outer ring 405 is in contact with a housing 417 via the insulating layer 415, the outer ring 405 and the housing 417 are insulated from each other. The insulating layer 415 prevents the flow of current from the housing 417 side to the inside of the bearing.
As illustrated in FIG. 18, Patent Document 1 proposes an insulated bearing having the above insulating layer 415, where edges 411a, 411b of the axial end surfaces 413A, 413B of the outer ring are chamfered. According to this insulated bearing, the axial end surfaces 413A, 413B of the bearing do not have sharp end portions. Therefore, sparks do not occur and electrolytic corrosion is prevented between the edge 411a of the axial end surface 413A and the housing 421 and between the edge 411b of the axial end surface 413B and the housing 417.